Mourinho is a psychologist, and this shows in how he handles his players differently. He knows who has a strong mentality, who is emotional, and who has an ego, and he treats them accordingly.
During his second spell at Chelsea, he hardly praised Cesc Fabregas in press conferences, but he always sent him a text message after most matches, to tell things like ‘ I know you’re good but not this good’ I can tell he gives Arda Guler that same Fabregas treatment today.
He understood that Eden Hazard wasn't a good trainer and was a bit egocentric, so he'd always promise him a day off if he had a good game and never got angry at his poor training.
Look at the way he handled Vini today, he understands that Vini is emotional, which is why he's 80% soft and 20% harsh toward him. I bet he wouldn't be that way toward Mbappé or Cucurella, players with a tougher mentality.
He gives each player different treatment based on their personality.